The book was opened at a special ceremony on Monday morning led by the Mayor of London Ken Livingstone and attended by Culture Secretary Tessa Jowell and Metropolitan Police commissioner Sir Ian Blair, as well as religious leaders.

Ms Jowell wrote: "The strength of London and her people is in diversity and tolerance. Our deepest sympathy is with the grieving families."

On Friday, on his return from the G8 summit in Gleneagles, the Prime Minister paid a visit to London Ambulance Service HQ in Waterloo Road where he congratulated staff on their response to the bombings.

• A two minute silence will be held on Thursday at 12 noon. It will be observed at Southwark Cathedral where the silence will be followed by prayers led by Canon Bruce Saunders.